Is market psychology important only when you are not trading a mechanical system? Doesn't a system take the psychology part out of it?

George,

There are a number of psychological factors which shape any investment decision-making process, many of which can exert an influence even in the design and implementation of systematic strategies.

A case in point is the well-known tendency of traders to focus on high-probability entry methods. William Eckhardt touches on this topic in New Market Wizards, and explains: "The problem in a nutshell is that human nature does not operate to maximize gain but rather to maximize the chance for a gain. The desire to maximize the number of winning trades (or minimize the number of losing trades) works against the trader. The success rate of trades is the least important performance statistic, and may even be inversely related to performance."

So in answer to your first question (â€œWhat's the difference between trading psychology and market psychologyâ€